Magazine Leaking (Gas Release Valve)

My magazine has been leaking for quite some time now, and I would like do try and fix it. I stuck each end in water, and it IS leaking from the top, not the bottom. Top being the side, where the gun pushes to release the gas. What can I do to fix this? I get around 2 shots, and maybe a 3rd where the slide doesn't even make it all the way back. If I put it up to my ear, I can hear the faint hissing. Any ideas?
Thanks,
Schuyler

EDIT: Also, I did lubricate the valve, taking it completely out of the magazine.

If it is leaking from the release valve. There are 3 ways to do this. But first you need to obtain a valve key to unscrew the release valve from the mag. Once you have the valve key you can do three things.

1. Poor man method - wrap the Teflon tape around the release valve and put it back in. Success rate is 50/50.

2. Home Depot method - replace o-rings on release valve. There are two of them.